What is an SRV Record?

An SRV (service) record is responsible for informing users of special services running under your domain.

For example, massivedns.com could have FTP access. So, instead of users manually entering the FTP details into their FTP client, the details can be stored directly in the domain name.

SRV records are accepted in the following format:

Format: _servicename._tcp.domainname.com (e.g. _ftp._tcp.massivedns.com)
Priority: 10 (if multiple SRV records are created, specify the priority)
Weight: 10
Port: 21 (e.g. the FTP port)
Destination: domainname.com (e.g. massivedns.com)

What is an MX Record?

MX records are responsible for providing the correct routing information for incoming mail of a domain.

For example, when a friend of yours sends an email to your domain, massivedns.com, your friend will lookup the MX records of the domain to find the correct location of your mail server.

Please be aware that an MX record must not contain an IP address, it must be a FQDN / Hostname (i.e. mail.massivedns.com or massivedns.com)
This can be achieved by creating an A record for massivedns.com or mail.massivedns.com, and then pointing your MX records to either location.

What is a CNAME Record?

A CNAME record (canonical or alias) maps a hostname to a hostname, e.g. (store.massivedns.com -> massivedns.com)

In the above example, anyone visiting ‘store.massivedns.com’ will be pointed to the root domain, ‘massivedns.com’.

This behaviour indicates that ‘store.massivedns.com’ is an alias of ‘massivedns.com’ (canonical).

Unlike A records or AAAA records, CNAME records only map to human readable addresses (not IP addresses)

What are Nameservers?

Nameservers are responsible for translating human-readable domain names (such as massivedns.com) into an IP address.

Nameservers are similar to address books, a person looks up the address (domain name) and the address book (nameserver) provides the location (IP address).

Each domain name must have a nameserver assigned in order for resolution to occur.

 

What are Glue Records / Child Nameservers / Private Nameservers?

Glue records are the binding (or glue) of IP addresses to your nameservers, e.g.

ns1.domain.com = 8.8.8.8
ns2.domain.com = 8.8.4.4

Glue records are held at the parent (GTLD / ccTLD / sGTLD) nameservers.

Example Scenario: Domain Nameservers Without Glue Records

Here’s an example scenario of a domain that does not have Glue records configured for its nameservers:

  1. [Guest] Hi, domain.com, what are your nameservers?
  2. [Host] Hi, Guest, my nameservers are ns1.domain.com and ns2.domain.com
  3. [Guest] Fantastic, I’ll head over there now. Could you provide me with the IP addresses so I can reach them?
  4. [Host] Sorry, I don’t know the IP addresses of the nameservers.
  5. [Guest] Okay, I’ll try ns1.domain.com and ns2.doman.com again.

Immediately, you will notice that the guest is now stuck in a loop as the IP addresses of the nameservers were not provided upon lookup.

Example Scenario: Domain Nameservers With Glue Records

Here’s an example scenario of a domain that has Glue records configured for its nameservers:

  1. [Guest] Hi, domain.com, what are your nameservers?
  2. [Host] Hi, Guest, my nameservers are ns1.domain.com and ns2.domain.com
  3. [Guest] Fantastic, I’ll head over there now. Could you provide me with the IP addresses so I can reach them?
  4. [Host] Sure, the IP addresses are 8.8.8.8 and 8.8.4.4.
  5. [Guest] Great, I’ve reached your nameserver IP’s and can query domain.com for its records

Now, we can see that the guest can successfully reach the nameservers because the exact locations (IP addresses) have been provided. The guest can now poll the nameserver for its appropriate records.

 

Example DNS Lookup

 

What is the difference between CNAME and A records, when should they be used?

Managing domain names can be challenging at the best of times. This tutorial is designed to clear up some of the confusion around the differences between CNAME and A (address) records.

Websites are served from locations that are uniquely identified by a group of numbers, which are known as IP addresses; but to access these sites we usually type in their corresponding domain names, which are easier to remember. To find the correct IP address, your browser will contact a Domain Name Server (DNS) and query its database for the IP address.

What is an A Record?

An A record is a record in these Domain Name Servers that links or maps a domain directly to its corresponding IP address.

For example, when you type mydomain.com into your browser, your browser will perform a DNS lookup which will return the corresponding IP address eg. 111.222.333.444.

Whas is a CNAME Record?

CNAME, or Canonical Name record, is a record that points to another domain address rather than an IP address.

For example, say you have several subdomains, like www.mydomain.com, ftp.mydomain.com,mail.mydomain.com etc and you want these sub domains to point to your main domain name mydomain.com. Instead of creating A records for each sub-domain and binding it to the IP address of your domain you can create CNAME records.

As you can see in the table below, in the case where the IP address of your server changes, you only need to update one A record and all the subdomains follow automatically because all theCNAMES point to the main domain with the A record:

(sub)Domain / Hostname Record Type Target / Destination
mydomain.com A 111.222.333.444
www.mydomain.com CNAME mydomain.com
ftp.mydomain.com CNAME mydomain.com
mail.mydomain.com CNAME mydomain.com

 

Examples of using CNAME records


Domains registered in different countries
CNAME records can also be handy in the case that you registered your domain name in several countries and you want to redirect them all to your main domain. For example mydomain.com.au and/or mydomain.co.nz can be redirected to mydomain.com

Products and brand names
In case you have registered several domain names, for example for your different products or brand names and you want to redirect them all to your main domain, you create CNAME recordsfor all these other domains. For example: myproduct.com > mydomain.com.

Limitations of CNAME records
1. Usage of CNAME records means that there is an additional request sent to the DNS servers, which can cause a delay of a few milliseconds.

2. You cannot create a CNAME record for the main domain name (mydomain.com) itself, this must be an A record.
For example, you cannot map mydomain.com to google.com, however, you can map google.mydomain.com to google.com.

3. MX or NS (nameserver) records may never point to a CNAME record, only A records.